Process for the manufacture of conducting polymers by treating polymeric compound containing basic groups with mixture of 7,7,8,8-tetracyanoquinodimethane and alpha,alpha,alpha&#39;,alpha&#39;-tetracyano-p-xylene



United States Patent U.s. (1260-895 Claims ABSTRACT OF THE DISCLOSURE Aprocess for the preparation of electrically conducting polymers, whereina polymeric material containing a plurality of basic groups in or on thepolymer chain, or a salt thereof, is treated with a mixture of7,7,8,8-tetracy-anoquinodimethane and a,a,a',a'-tetracyano-p-xylene.

This invention relates to a polymer process, more especially for thepreparation of conducting polymers.

' We have found that the electrical conductingproperties of a polymercontaining a plurality of basic groups, or a salt thereof, areconsiderably enhanced upon treatment with a mixture of7,7,8,8-tetracyanoquinodimethane and a,a,a',a-tetracyano-p-xylene.

Thus, according to the present invention, we provide a process for thepreparation of electrically conducting polymers, wherein a polymericmaterial containing a plurality of basic groups in or on the polymerchain, or a salt thereof, is treated with a mixture of7,7,8,8-tetracyanoquinodimethane and a,a,m',a'-tetracyanopxylene.

The polymeric materials suitable for treatment according to the'processof our invention are those containing a plurality of basic groups in oron the polymer chain, including homopolymers, copolymers, and blends andmixtures thereof. 7

Examples of polymeric materials, and salts thereof,

suitable for the process of our invention include the homopolymers andsalts, and copolymers and salts of 2-vinylpyridine,N,N-diethylamin-oethylmethacrylate, N,N- dimethylaminoethylmethacrylate,vinyl-N,N-diethylaminoacetate and ethyleneimine, for example thehomopolymers poly(2-vinylpyridine),poly(N,N-diethylaminoethylmethacrylate), poly(N,Ndimethylaminoethylmethacrylate), poly(vinyl N,N diethylaminoacetate) andpolyethyleneimine, the copolymer of styrene and 2-vinylpyridine, and theiodide, sulphate and methosulphate of poly(l-methyl-Z-vinylpyridine) andof poly(1-n butyl-2- vinylpyridine), and blends or mixtures of suchhomopolymers, copolymers and salts, for example a blend ofpoly(2-vinylpyridine) and poly (N,N-dimethylaminoethylmethacrylate) The7,7,8,S-tetracyanoquinodimethane is the compound also known as7,7,8,S-tetracyanoquinonedimethane, and is represented by the followingFormula I, which has no 'steric significance: i

The 7,7,8,8-tetracyanoquinodimethane will hereinafter be referred to asT CNQ.

The a,a,a',a-tetracyano-p-xylene is the compound also known asp-phenylenedimalononitrile, and is represented by the following FormulaII, which has no steric significance:

II HC( )2 The a,a,m',a'-tetracyano-p-xylene may be prepared by theaction of a mild reducing agent on TCNQ, for example by the reaction ofTCNQ with mercaptoacetic acid (SH-CH COOH) in glacial acetic acid underreflux conditions as described by Acker and Hertler (Journal of theAmerican Chemical Society, 1962, 84, 3370).

The a x,a',a'tetra-cyano-p-xylene will hereinafter be referred to as HTCNQ.

For the process of our invention we have found that TCNQ and H TCNQ inthe ratios of 1 to 3 moles of TCNQ per mole of H TCNQ are preferred.Molar ratios of TCNQ to H TCNQ outside this range may be used, ifdesired, although it may be found that reduced conductivities areobtained thereby. It is preferred to use molar proportions of TCNQ to HTCNQ in the range 2: 1 to 3:1 for best results.

The polymer is preferably present in the proportions of from 2 to 6moles of polymer basic unit, or salt thereof, per mole of H TCNQ. Largeror smaller proportions of polymeric base, or salt thereof, may be used,although this may not achieve any advantage as far as the electricalconducting properties of the resultant polymers are concerned and mayeven result in lower conductivities. It is preferred to use theproportion of 2 moles of polymer basic unit, or salt thereof, per moleof H TCNQ, to give the best conductivities.

The process of our invention is best carried out in solution. Suitablesolvents are those in which the polymer, TCNQ and the H TCNQ are allsoluble. Examples include dimethylformamide, mixtures of acetonitrileand ethanol, acetonitrile and chloroform, acetonitrile and water(suitable when the polymer is in the form of its salt), and benzene.

It has been found particularly advantageous to use a solvent in whichthe product of the reaction is also soluble, for exampledimethylformamide. It has also been found advantageous, for economicreasons, to use the minimum amount of solvent necessary to give completesolution of the reactants at the reaction temperature, but greaterquantities of solvent may be used, if desired.

The temperature for the reaction is not critical, and it has been foundconvenient to carry out the reaction at room temperature. However, incertain cases, particularly where solvents other than dimethylformamideare being used, higher temperatures may be required to maintain thestarting materials in solution. In general, temperatures up to thereflux temperature of the reaction mixture may be used without detrimentto the properties of the product.

The process may be effected at substantially atmospheric pressure.

It has been found advantageous to conduct the process in the substantialabsence of air, for example by employing an atmosphere of inert gas, forexample, nitrogen, throughout the process. By an inert gas we mean onewhich does not react with any of the other compounds used in thisprocess.

The time required for reaction is dependent on various factors,including the particular polymeric base used as aistarting material andthe concentrations of reactants. In most cases, however, the reaction isquick, and, in general, reaction times within the range /2 hour to 2hours have been found sufficient and shorter reaction times may beadequate in some circumstances.

, The polymers resulting from the process, as herein described, may beisolated by conventional techniques, for example by pouring the reactionmixture into a liquid in which. the polymer is,insoluble or onlysparingly soluble, for example diethyl ether, by distilling off thesolvent, or, where solvents have been used wherein the product isinsoluble or only sparingly soluble, by filtering oil the precipitatedproduct. Care should be exercised in choosing the nornsolvents as manymay be found to have a detrimental effect on the conductivities of theproducts. We have found diethyl ether to be satisfactory.

In. the preferred embodiment of our invention the polymeric. base isdissolved in dimethylforrnamide and treated with a mixture of TCNQ and HTCNQ in dimethylformamide solution, under an atmosphere of nitrogen.

The proportions are preferably 2 moles of polymer basic unit, to 1 moleof H TCNQ to 2 to 3 moles of TCNQ. The mixture is allowed to react forfrom /2 hour to 2 hours after which time the polymer is isolated bypouring the reaction mixture into diethyl ether and filtering oif theprecipitate.

The polymers produced according to the process of our invention areelectrically conducting. For example, with poly(2-vinylpyridine) as thestarting material, a polymer of conductivity 1.9l 10- mho cm? may beobtained, with poly (1-methyl-2-vinylpyridinium iodide) as the startingmaterial, a polymer of conductivity 1.7 10- mho cm.- may be obtained,and with the copoly-mer of styrene and 2-vinylpyridine as the startingmaterial, a polymer of conductivity 2.84 1 mho cm. may be obtained. Byway of comparison, the untreated polymeric bases all have conductivitiesconsiderably less than mho cm.-

It is preferred to store the polymers in the absence of air, for examplein an inert atmosphere, for example nitrogen, to avoid any loss inconductivity which may be found to occur on exposure to air.

Such polymers may be used, for example, as conducting films for heatingpanels. It is preferred that the polymers be protected from air in use,for example by encapsulation in suitable polymeric material, for exampleMelinex (registered trademark) polyester film.

The invention is illustrated, but not in any way limited, by thefollowing examples, in which all proportions are in parts by weightunless otherwise stated.

In the examples, all the conductivities quoted were measured by thefour-point probe method as described by L. B. Valdes (Proceedings of theInstitute of Radio Engineers (1954), 42, 420427) on compressed discs ofpolymer powder at C.

Example 1 A mixture containing H TCNQ (103 parts, 1 equivalent), TCNQ(204 parts, 2 equivalents) and dry dimethylformamide (4,750 parts) washeated to 100 C. whilst agitated by a stream of dry nitrogen in areaction vessel provided with a reflux condenser, a tap funnel, and anitrogen bleed tube. Heating was carried out on an oil bath.

Atactic poly(2-vinylpyridine), having an intrinsic viscosity at C. inethanol of 1.76 decilitresgm. and a molecular weight, measured by alight scattering method using benzene as solvent, of 1,'730,000-. 50,000(105 parts, 2 equivalents) was dissolved in dry dimethylformamide (2,500parts) and the resulting solution was introduced into the reactionvessel via the tap funnel. The dark green solution produced was heatedquickly to its reflux temperature (150 C.) and maintained at thistemperature for minutes, after which time it was allowed to cool to roomtemperature. The cooled solution was poured 4 into dry, peroxide-freediethyl ether (distilled from calcium hydride) (21,450 parts). Ablue-black solid precipitated leaving a green supernatant liquid. Thesolid was removed by filtration, washed with dry diethyl ether until thewashings were colourless, dried under vacuum for 1 hour at roomtemperature and then for a further 16 hours at 48 C.

346 parts of a product were obtained having a decomposition range of 184C.202 C. and a conductivity of 1.91 10 mho, cm.-

Example 2 Isotactic poly(2-vinylpyridine), having an intrinsicviscosity, measured in dimethyl formamide at 25 C., of 0.64 decilitresgm. and a crystallinity, as determined by X-ray diifraction, of 35%,prepared according to the method described by Natta, Mazzanti, Longi,'Dallasta and Beruadini in J. Polymer Science (1961), 51, 487, parts, 2equivalents), was dissolved in air-free dimethylformamide (2,500 parts)and was added with stirring under an atmosphere of nitrogen to asolution of H TCNQ (103 parts, 1 equivalent) and TCNQ (102 parts, 1equivalent) in dimethylformamide (5,000 parts) maintained at 20 C.

The mixture rapidly formed a gel and anhydrous, peroxide-free diethylether (distilled from calcium hydride) (18,000 parts) was added to thestirred mixture to give a bluish-black precipitate. The solid materialwas collected by filtration under an atmosphere of nitrogen, washed withether until the washings were colourless and dried under vacuum at 45 C.

The product (265 parts) melted over the range 164- 180 C., with slightdecomposition at C. and had a conductivity of 6.22 10 v mho cm." and amagnetic susceptibility of 0.903 10 e.m.u. per gram.

Example 3 'Isotactic poly(2-vinylpyridine) (105 parts, 2 equivalents)was treated with a mixture of TCNQ (204 parts, 2 equivalents) and H TCNQ(103 parts, 1 equivalent following essentially the same \procedure asthat described in Example 2. 335 parts of a black powder were obtainedwhich melted over the range 165-184 C., with some decomposition over therange 122-130" C. The product had a conductivity of 1.7 10- mho !cm.*and a magnetic susceptibility of 1.062. 1O e.m.u. per gram.

Example 4 parts (3.3 equivalents) of actactic poly(2- vinylpyridine),having an intrinsic viscosity measured in ethanol at 25 C., of 1.76decilitres gm.- in which 37.7% of the basic groups had been quaternishedby treatment with n-butyl iodide, were dissolved in dimethylformamide(10,000 parts) and the solution was added to a stirred mixture of H TCNQ-(52 parts, 1 equivalent), TCNQ (153 parts, 2.5 equivalents) anddimethylformamide (8,000 part). The reaction mixture was maintained at atemperature of 80 C. under an atmosphere of nitrogen during the additionand for a further period of 1 hour.

The reaction mixture was then cooled to room temperature and poured intodry, peroxide-free diethyl ether (distilled from calcium hydride) (35,000 parts) when a black solid was precipitated. The product was isolatedby filtration, washed with ether until the washings were colourless anddried under vacuum.

250 parts of a product were obtained, melting over the range 173-194 C.and having a conductivity of 1.2 10 mho cm.

Example 5 Atactic poly(2-vinylpyridine), having an intrinsic viscosity,measured in ethanol at 25 C., of 1.76 decilitres gmf (12 6 parts, 6equivalents) was treated with TCNQ (122 parts, 3 equivalents) and H TCNQ(41 parts, 1 equivalent) by the procedure described in Example 4,

except that a reaction time of /2 hour was employed.

220 parts of a black, amorphous powder were obtained having a meltingpoint of 181 C. and a conductivity of 2.1 X mho cmf Example 6 105 parts(2 equivalents) of a copolymer, having an intrinsic viscosity measuredin chloroform .at C., of 1.484 decilitres gmr derived from styrene (51.6mole percent) and 2-vinylpyridine 48.4 mole percent) were dissolved indimethylformamide (5,000 parts) and added to a stirred mixture of H TCNQ(52 parts, 1 equivalent) and TONQ (153 parts, 3 equivalents). Thereaction mixture was maintained at 80-100 C. under nitrogen during theaddition and then for a further minutes.

The resulting dark green solution was cooled at 20 C. and poured intodry, peroxide-free diethyl ether (distilled from calcium hydride)(35,000 parts) when a black solid was precipitated leaving a dark greensupernatant liquid. The product was filtered 01f, washed thoroughly withether and dried in a vacuum. 280 parts of a product were obtainedmelting over the range 185-2 07 C. and having a conductivity of 2.9 10mho cmf Example 7 Poly(N,-N dimethylaminoethylmethacrylate) 105 parts, 2equivalents) was dissolved in dimethyl'formamide (5,000 parts) under anatmosphere of nitrogen and added, at a temperature of 8090 C., to astirred mixture of H TCNQ (69 parts, 1 equivalent), TCNQ (204 parts, 3equivalents) and dimethylformamide (5,000 parts), the reaction mixturebeing maintained at 90 C. for a fun ther one hour.

The resulting dark green solution was cooled to 20 C. and poured intodiethyl ether (distilled from calcium hydride) (22,000 parts) to give avery dark blue-green solid which was filtered off under nitrogen, washedthoroughly with air-free ether and dried under vacuum at 50 C.

280 parts of a powder were obtained having a conductivity of 1.43 X 10-mho cmf Example 8 A mixture of poly(2-vinylpyridine) (53 parts, 1equivalent) and poly(N,N-dimethylaminoethylmethacrylate) (79 parts, 1equivalent) was dissolved in dimethylformamide (5,000 parts) and thesolution added, at a temperature of 8090 C., to a stirred solution of HTCNQ (103 parts, 1 equivalent) and TCNQ (255 parts, 2.5 equivalents) indimethylformamide (5,000 parts). The mixture was maintained at 90 C.,under nitrogen for 1 hour.

The solution was then allowed to cool to room temperature and pouredinto excess diethyl ether, distilled from calcium hydride, to give ablue-black solid which was filtered ofl, washed with ether, and driedunder vacuum at 50 C.

380 parts of a product were obtained having a conductivity of 1.62 10mho cmf Example 9 To a stirred mixture of H TCNQ (52 parts, 1equivalent) and TCNQ (153 parts, 3 equivalents), dissolved indimethylformamide (2,500 parts) and heated to 90 C. under nitrogen, wasadded a solution of poly(vinyl- N,N diethylaminoacetate) (79 parts, 2equivalents) in dimethylformamide 5,000 parts). The mixture wasmaintained at 90 C. for one hour, then cooled to 20 C. and poured intoexcess, dry, peroxide-free diethyl ether, distilled from icalciumhydride. The resulting purpleblack precipitate was collected byfiltration, Washed with ether and dried under vacuum at 50 C.

205 parts of a dark green-blue solid were produced, having aconductivity of 3.4 10 mho cmr 6 Example 10 A mixture of H TCNQ (52parts, 1 equivalent) and TCNQ (102 parts, 2 equivalents), under anatmosphere of dry nitrogen, were dissolved in boiling dry acetonitrile(10,000 parts) and, when complete dissolution was obtained, ethanol(2,000 parts) was added. To this solution were added 53 parts (2equivalents) of atactic poly(2- vinylpyridine), having an intrinsicviscosity in ethanol at 25 C. of 1.27 decilitres gmf in solution in anearly boiling mixture of acetronitrile (5,000 parts) and ethanol (1,500parts).

The resulting homogeneous, dark green solution was boiled under reflux.After 5 minutes a dark solid began to separate out, and after 30 minutesthe mixture was cooled and the resulting black, gelatinous mass wascollected by filtration, washed with acetonitrile and then with diethylether and dried. 137 parts of a product were obtained, melting over therange 178-186 C. and having a conductivity of 2.25 x 103 mho cmr Example11 A mixture of H TCNQ (52 parts, 1 equivalent) and TCNQ (102 parts, 2equivalents) was dissolved, under nitrogen, in a boiling mixture of.acetonitrile (10,000 parts) and chloroform (22,500 parts). To thissolution (here was added a copolymer (105 parts, 2 equivalents) ofstyrene (51.6 mole percent) and 2-vinylpyridine (48.4 mole percent)dissolved in chloroform (1,500 parts) and acetonitrile (500 parts). Ablack gelatinous precipitate separated out from the reaction mixture,and was collected by filtration, washed with diethyl ether, and driedunder vacuum.

A black, amorphous solid (178 parts) was obtained, melting above 300 C.and having a conductivity of 4 10 mho cmr Example 12 Atacticpoly(2-vinylpyridine) having an intrinsic viscosity, measured in ethanolat 25 C., of 1.76 decilitres gm.- (105 parts, 2 equivalents) wasdissolved in benzene (8,800 parts) and the solution was added to astirred mixture of H TCNQ 103 parts, 1 equivalent), TCNQ (204 parts, 2equivalents) and benzene (8,800 parts) at C. under nitrogen. The mixturewas boiled under reflux for 30 minutes and then the solvent wasdistilled 01f leaving a solid residue having a melting point of 179 C.and a conductivity of 137x10 mho cmf Example 13 Atacticpoly(2-vinylpyridine), having an intrinsic viscosity, measured inethanol at 25 C. of 1.27 decilitres gmr' was quaternised with methyliodide to give poly(lmethyl-2-vinylpyridinum iodide) in which 76.1% ofthe nitrogen atoms were alkylated. 124 parts (2.3 equivalents) of thisproduct were dissolved in water (3,000 parts) and added to a mixture ofH TCNQ (52 parts, 1 equivalent), TCNQ (153 parts, 3 equivalents) andacetonitrile (8,000 parts) boiling in an atmosphere of nitrogen. Theresulting solution was boiled under reflux for 2 hours, cooled to 20 C.and the black gel which separated was filtered oif, washed withacetonitrile and then diethyl ether and dried under vacuum at 40 C.

A dark green solid (243 parts) was obtained, melting at 187 C. andhaving a conductivity of 2.13 10 mho cmf Example 14 A solution ofpoly(1-methyl-Z-vinylpyridinium iodide) (as employed in Example 13) (58parts, 2.2 equivalents) in dimethylfor'rnamide (2,000 parts) was added,under nitrogen, to a solution of H TCNQ (26 parts, 1 equivalent) andTCNQ (77 parts, 3 equivalents) in dimethylformamide (4,000 parts) at atemperature of C. The mixture was maintained at 85 C. for hour and thenpoured into stirred diethyl ether (distilled from calcium hydride)(14,280 parts) to give a dark, green-blue precipitate which was filteredoff, washed with diethyl ether and dried under vacuum at 45 C.

83 parts of a product were obtained, melting over the range 171-177 C.and having a conductivity of 1.7 mho crnr Example To a solution of HTCNQ (52 parts, 1 equivalent) and TCNQ (102 parts, 2 equivalents) indimethylfor-mamide (3,000 parts,) heated to 80-90 C. under an atmosphereof nitrogen was added a solution of 53 parts (2 equivalents) of atacticpoly(2-vinylpyridine), having an intrinsic viscosity measured in ethanolat 25 C. of 1.76 decilitres gm.- in dimethylformamide (2,500 parts). Themixture was heated for hour at 90 C., allowed to cool and poured intodiethyl ether (distilled from calcium hydride) (18,000 parts). Theprecipitate fromed was filtered off, washed with diethyl ether and driedunder vacuum at'45 C. A purple, amorphous product (160 parts), Wasobtained, melting at 184 C., and having a conductivity of 1 10 mho cmfExample 16 To a stirred, cold solution of H TCNQ (103 parts, 1equivalent) and TCNQ (204 parts, 2 equivalents) in dimethylformamide(5,000 parts), maintained at 20 C. under an atmosphere of nitrogen, wasadded a solution of atactic poly(2-vinylpyridine) having an intrinsicviscosity measured in ethanol at C., of 1.76 decilitres gmr (105 parts,2 equivalents) in dimethylformamide (3,000 parts). The mixture rapidlyformed a gel to which dry, peroxide-free diethyl ether (distilled fromcalcium hydride) (18,000 parts) was added with agitation to give ablue-black precipitate which was filtered otf, washed with diethyl etheruntil the washings were colourless and dried under vacuum.

The product (343 parts) had a conductivity of 1.68x10- mho cm. and amagnetic susceptibility of 0.729 10- e.m.u. per gram.

What we claim is:

1. A process for the preparation of electrically conducting polymerswherein a polymeric material containing a plurality of basic groups iscontacted with a mixture of 7,7,8,8-tetracyanoquinodimethane anda,a,oc',ct'- tetracyano-p-xylene.

2. A process according to claim 1 wherein the molar ratios of7,7,8,S-tetracyanoquinodimethane to u,cc,cc',a' tetracyano-p-xylene arein the range 1:1 to 3:1.

3. A process according to claim 2 wherein the molar ratios of7,7,8,8-tetracyan0quinodirnethane to u,a,u,a',- tetracyano-p-xylene arein the range 2:1 to 3:1.

4. A process according to claim 1 wherein the molar ratios of polymerbasic units to a,a,a',a',-tetracylano-p xylene are in the range 2: 1 to6: 1.

5. A process according to claim 4 wherein the molar ratio of polymerbasic units to a,a,a',a,-tetracyano-pxylene is 2:1.

6. A process according to claim 1 when effected in the presence of aliquid medium which is a solvent for the polymer base, the7,7,8,S-tetracyanoquinodimethane and the 11,0,a,d-tetracyano-p-xylene.

7. A process according to claim 6 wherein the liquid medium is selectedfrom the group consisting of dimethyl formamide, benzene, a mixture ofacetonitrile and ethanol, a mixture of acetonitrile and chloroform and amixture of acetonitrile and water.

8. A process according to claim 1 when effected under an atmosphere ofnitrogen.

9. A process according to clai is isolated by pouring the reactionmixture into diethyl ether.

10. A process according to claim 1 wherein the polymeric materialcontaining a plurality of basic groups is selected from the groupconsisting of poly(2-vinylpyridine), poly(N,Ndimethylaminoethylmethacrylate, poly(vinyl-N,N-diethylaminoacetate), acopolymer of styrene and 2-vinyl-pyridine and a blend of poly(2-viny1-pyridine) and poly(N,N dimethylaminoethylmethacrylate).

References Cited UNITED STATES PATENTS 3,346,444 10/1967 Lupinski et al.161-213 JAMES A. SEIDLECK, Primary Examiner.

C. A. HENDERSON, JR., Assistant Examiner.

U.S. Cl. X.R.

m 1 wherein a product

